[colm] Add CMake project

[Konstantin Podsvirov]

Hello Adrian Thurston and list!

My name is Konstantin.

What about adding cross-platform build system like CMake (https://cmake.org)?

This will help to solve the problem of porting the project on a non Unix-like systems.

I have some ideas and results as well.

You can see the proposed changes in your browser:

http://git.podsvirov.pro/?p=dad/fix/colm.git;a=commitdiff;h=cmake

Or download using the version control system (branch `cmake`):

git clone -b cmake git://podsvirov.pro/dad/fix/colm.git

Here are my first results.

Now implemented:
- Bootstrap `colm` program from sources;
- Install target `colm::coml` and `colm::libcolm`
  via CMake's `colm` package.

Shadow build support via CMake.

Tested with MSYS2 and MinGW-w64 on Windows and with GCC on Linux.

Detected issue when sizeof(word_t) < sizeof(void*).

I want to see if I had kindred spirits and should I continue 
this activity?

Any questions and suggestions?

Sorry for mistakes in text (I use translator).

--
Regards,
Konstantin Podsvirov